Hello everybody! 
Problem is: I'm so tired about poor performance from triode amplifiers. Poor damping factors and high distortion even at low volumes are an issue. I know, a 300B PP amp is one of the best sound I've ever heard, and it also measure quite well, but 300B are too expensive.
So my interest recently moved toward the great amplifiers from the past.
I would like to collect information about them, how did they sound, focusing on what are the technical "tricks" that they used (back in the days were audio meant research).
I'm talking about Quad II, Leak, McIntosh, H/K Citation, etc etc...
What's good in them, and what can be still succesfully used those days to build good performing amps.
- triode / tetrode-pentode / ultralinear?
- what kind of negative feedback?
etc etc... and please post schematics of the amp you're talking about.
Thanks in advance to everyone.
Problem is: I'm so tired about poor performance from triode amplifiers. Poor damping factors and high distortion even at low volumes are an issue. I know, a 300B PP amp is one of the best sound I've ever heard, and it also measure quite well, but 300B are too expensive.
So my interest recently moved toward the great amplifiers from the past.
I would like to collect information about them, how did they sound, focusing on what are the technical "tricks" that they used (back in the days were audio meant research).
I'm talking about Quad II, Leak, McIntosh, H/K Citation, etc etc...
What's good in them, and what can be still succesfully used those days to build good performing amps.
- triode / tetrode-pentode / ultralinear?
- what kind of negative feedback?
etc etc... and please post schematics of the amp you're talking about.
Thanks in advance to everyone.
I don't quite understand...I always thought (read) that triode amplifiers have higher damping factors than pentodes - that's why a PP amp with EL34 in triode can play without feedback, while EL34 in pentode will need some. That's already one point: making good use of negative feedback will increase damping factor!
Distortion is an issue with SE (which were your interest in some recent threads) but I see that the Red Light and others show good distortion figures and the employed tubes don't cost as much as 300B's. Better distortion figures may be reserved to SS terrain.
Here I am again recomending Morgan Jones Valve amplifiers third edition, where he explains the Williamson, the Quad II and a mullard design (5-20, if I am not mistaken). And after reading the problems with those circuits you will probably like his crystal palace!
Distortion is an issue with SE (which were your interest in some recent threads) but I see that the Red Light and others show good distortion figures and the employed tubes don't cost as much as 300B's. Better distortion figures may be reserved to SS terrain.
Here I am again recomending Morgan Jones Valve amplifiers third edition, where he explains the Williamson, the Quad II and a mullard design (5-20, if I am not mistaken). And after reading the problems with those circuits you will probably like his crystal palace!
Damping factor is only one performance critereon. Besides, the damping factor without feedback is only worth looking at if you're running without feedback; one of the beauties of pentode operation is that one can achieve quite low distortion and good damping because of the high open loop gain. (It's also possible to get a very bad result if you don't know what you're doing!)
The analyses by Morgan Jones in Valve Amplifiers are excellent! One thing becomes clear, though: many engineering decision in classic amps were made for cost reasons. Others were made because of the economics and size of components in that era, which may or may not be applicable now (e.g., good active regulators were bulky and expensive in 1960, but not so today). There's a weird current in the tube community which takes the unexceptional idea that not all newer technologies are better and transmutes it into the idea that NO newer technology is better. The Crystal Palace is a perfect refutation of that silly notion, making appropriate use of LEDs, chips, bipolars, and the like to achieve performance that would have been prohibitive 40 years ago.
The analyses by Morgan Jones in Valve Amplifiers are excellent! One thing becomes clear, though: many engineering decision in classic amps were made for cost reasons. Others were made because of the economics and size of components in that era, which may or may not be applicable now (e.g., good active regulators were bulky and expensive in 1960, but not so today). There's a weird current in the tube community which takes the unexceptional idea that not all newer technologies are better and transmutes it into the idea that NO newer technology is better. The Crystal Palace is a perfect refutation of that silly notion, making appropriate use of LEDs, chips, bipolars, and the like to achieve performance that would have been prohibitive 40 years ago.
This is a heretofore unknown discovery.
Seriously, the key to a good performing amp isn't whether you use a triode or pentode, but how much development time you put into the design involving both measuring and listening. I've heard all kinds of tube amps and the most highly developed (read engineered) ones almost always sound best. I personally like in this order:
Single ended DHT
Push-pull DHT
Push-pull Ultralinear
The differences are minimal in well-designed and well-developed systems and each type has its strong points. In other words, you can't expect good performance fiddling around with SPICE and throwing something together in one shot.
John
There's no trick. Guys like SY can improve on most of those amps you mentioned. At least as far as measurements go. There probably won't be any sonic difference.
Japanese audio gurus tend to rate pre war stuff as the best ever made. And it mainly comes down to the output transformers. I might have posted this earlier. The Western Electric 111C repeat coil has a ruler flat resonse from about 28-28,000 Hz. It was designed to balance lo-fi phone lines in the 1930s. Some WE and UTC audio transformers have much better specs than that. I recently saw a single WE OT priced at $1,800 on eBay. I don't agree with the price. But I can at least understand why.
I sold a pair Telefunken pro audio step-up/balancing transformers from 1964 to a Reimyo PAT777 owner in the US as an upgrade to his Shindo step-up transformers. I was a bit worried about sending them across the pond. I was afraid they wouldn't be an improvement in his system, which is much better than mine. He convinced me, saying he was willing to take a chance. He was very happy with the transformers, saying the highs are much more open and detailed. Now, I have only owned vintage step-up transformers. But from his and other reports, I'm positively sure that you won't find a modern step-up transformer that can hold a candle to those beefy (close to 500 grams) Telefunkens.
Sorry for the rant.
Japanese audio gurus tend to rate pre war stuff as the best ever made. And it mainly comes down to the output transformers. I might have posted this earlier. The Western Electric 111C repeat coil has a ruler flat resonse from about 28-28,000 Hz. It was designed to balance lo-fi phone lines in the 1930s. Some WE and UTC audio transformers have much better specs than that. I recently saw a single WE OT priced at $1,800 on eBay. I don't agree with the price. But I can at least understand why.
I sold a pair Telefunken pro audio step-up/balancing transformers from 1964 to a Reimyo PAT777 owner in the US as an upgrade to his Shindo step-up transformers. I was a bit worried about sending them across the pond. I was afraid they wouldn't be an improvement in his system, which is much better than mine. He convinced me, saying he was willing to take a chance. He was very happy with the transformers, saying the highs are much more open and detailed. Now, I have only owned vintage step-up transformers. But from his and other reports, I'm positively sure that you won't find a modern step-up transformer that can hold a candle to those beefy (close to 500 grams) Telefunkens.
Sorry for the rant.
Hi Giame, what caused you to arrive at that conclusion? Of the output tubes I've tested, from EL84 to the 8XX series of transmitter tubes, triode has always yielded lower distortion, much reduced high order distortion harmonics, and much better damping factor. On one occasion though, an old Mullard circuit, conversion from pentode to triode operation raised the distortion and killed the top end. The driver was marginal and couldn't handle the extra grid capacitance of a triode-connected output tube.
That's not to say pentode can't make for an excellent amp. Like SY says, the increased ca be put to good use in the feedback loop.
That's not to say pentode can't make for an excellent amp. Like SY says, the increased ca be put to good use in the feedback loop.
Hello everyone,
thank you for your interesting replies.
Maybe I had to me clearer in my request, I see that.
So the problem is: I will have, in the near future, to build an amp for a friend who has 92dB Tannoy 38cm dual concentric speakers (actually, they are the Mainsfeld, an infinite baffle cabinet).
We listened to various amplifiers, including those "pentode/tetrode PP with negative feedback" kind of amplifiers. So as you can guess we decided for them, because triode amplifier don't cut it (we need almost sand-state damping factor, and more than 20W) but in general we didn't like solid state amps with them. And he didn't like the sound of the Ming-Da amp.
And to me it seems more "historically correct" (probably this is the whole point) to drive them with tube amplifiers of their era.
So my interest was in understanding which was, for your opinion, the best amplifier to be built (custom made transformers, and yes, maybe I can have done some complex transformers with cathode feedback windings and the like, that seemed to be "en vogue" in that era).
Maybe if I make a list of the possibilities, it will be easier:
- the Williamson here ;
- Leak TL-12 here ;
- Quad II here ;
- this one ;
- the Mc275 here ;
- the C/J MV75 here ;
- the Dynaco Mark III here ;
- the H/K Citation II here ;
- the Dynaco Mark IV here ;
- the Marantz 9 here ;
- the Mc240 here ;
- this one ;
So thanks to everyone that wants to share his experience with those designs (or similar ones).
Thanks again!
thank you for your interesting replies.
Maybe I had to me clearer in my request, I see that.
So the problem is: I will have, in the near future, to build an amp for a friend who has 92dB Tannoy 38cm dual concentric speakers (actually, they are the Mainsfeld, an infinite baffle cabinet).
We listened to various amplifiers, including those "pentode/tetrode PP with negative feedback" kind of amplifiers. So as you can guess we decided for them, because triode amplifier don't cut it (we need almost sand-state damping factor, and more than 20W) but in general we didn't like solid state amps with them. And he didn't like the sound of the Ming-Da amp.
And to me it seems more "historically correct" (probably this is the whole point) to drive them with tube amplifiers of their era.
So my interest was in understanding which was, for your opinion, the best amplifier to be built (custom made transformers, and yes, maybe I can have done some complex transformers with cathode feedback windings and the like, that seemed to be "en vogue" in that era).
Maybe if I make a list of the possibilities, it will be easier:
- the Williamson here ;
- Leak TL-12 here ;
- Quad II here ;
- this one ;
- the Mc275 here ;
- the C/J MV75 here ;
- the Dynaco Mark III here ;
- the H/K Citation II here ;
- the Dynaco Mark IV here ;
- the Marantz 9 here ;
- the Mc240 here ;
- this one ;
So thanks to everyone that wants to share his experience with those designs (or similar ones).
Thanks again!
Hi Giaime
So you are saying you tried PP amps witrh triodes and those did not have sufficient damping factor? What kind of triodes? Did you use the same amp, with the pentodes wired as triodes?
Morgan Jones, yes, he again, mentions that open baffle speakers and low damping factor could be a very good combination. He elaborates on this, but I don't remember the technical aspect right now...
Other people can help you better - and I am leaving for the Sziget festival, curious how this thread develops during this week!
Erik
So you are saying you tried PP amps witrh triodes and those did not have sufficient damping factor? What kind of triodes? Did you use the same amp, with the pentodes wired as triodes?
Morgan Jones, yes, he again, mentions that open baffle speakers and low damping factor could be a very good combination. He elaborates on this, but I don't remember the technical aspect right now...
Other people can help you better - and I am leaving for the Sziget festival, curious how this thread develops during this week!
Erik
I do not think vintage transformers automatically are good. But the good ones are still as impressive today as they were in the 1930s.
The eBay seller of these UTC LS-30s says the frequency response is 7 to 50,000 Hz. That doesn't say much. UTC's catalogs from the 1940s say the response is 20-20k, +/- 1db. That's pretty good.
The eBay seller of these UTC LS-30s says the frequency response is 7 to 50,000 Hz. That doesn't say much. UTC's catalogs from the 1940s say the response is 20-20k, +/- 1db. That's pretty good.
ErikdeBest, I follow you.
As for my own amp, it's from the 1960s. So while I like it, it's too new to have to-die-for OTs. It's probably a "very good example of compromises that had to be made 40 years ago."
But the thing is, I paid something like €400. Should I buy an equal new amp, it will cost €4,000. I wouldn't mind upgrading to a 1930s WE or Klangfilm amp. But then we're again talking thousands and not hundreds. So I'm not complaining a lot.
As for my own amp, it's from the 1960s. So while I like it, it's too new to have to-die-for OTs. It's probably a "very good example of compromises that had to be made 40 years ago."
But the thing is, I paid something like €400. Should I buy an equal new amp, it will cost €4,000. I wouldn't mind upgrading to a 1930s WE or Klangfilm amp. But then we're again talking thousands and not hundreds. So I'm not complaining a lot.
I'll be of no help then. My 12" Tannoy Golds are driven hours a day by a trioded EL84 while my parts-upgraded Mc240 sits beneath the TV unpowered looking pretty.
phn, check the impedance ratios. 50 KHz is pretty good but no great shakes for a unity (600:600 to 50:50, seller doesn't specify which connection) transformer. The Hammond 804's used in telephony equipment will approach that performance at somewhat less max power. To my knowledge those impedances also make it useless in tube circuits save for specialized applications, for example as an input transformer driven by a low impedance source.
Not saying there isn't some good old iron out there either but by and large 40 years of computer modelling really has resulted in typically superior performance. Check the roughly equivalent spec (ratios and max power) Cinemag. It's flat past 200 kHz:
http://www.cinemag.biz/output/CMOB-3.pdf
phn, check the impedance ratios. 50 KHz is pretty good but no great shakes for a unity (600:600 to 50:50, seller doesn't specify which connection) transformer. The Hammond 804's used in telephony equipment will approach that performance at somewhat less max power. To my knowledge those impedances also make it useless in tube circuits save for specialized applications, for example as an input transformer driven by a low impedance source.
Not saying there isn't some good old iron out there either but by and large 40 years of computer modelling really has resulted in typically superior performance. Check the roughly equivalent spec (ratios and max power) Cinemag. It's flat past 200 kHz:
http://www.cinemag.biz/output/CMOB-3.pdf
Hello Erik,
We tried some DIY and commercial stuff in the last months. Ming-Da 300B PP and a DIY 2A3 PP, some chinese 845 amp, DIY EL34 triode PP amp. No, we didn't try the same amp changing output tube mode of operation, because I think that an amplifier has to be designed for a choosen operation, and optimized for it. In fact, wiring in triode mode a Ming-Da EL34 PP (that was UL) sounded worse.
We even tried the ugly mono-channel prototype of my EL36 triode amp
Those are infinite baffle speakers. I'm not so expert in speakers matters, but as I understand that's not a "tube friendly" enclosure such as horn speakers (also because of lower efficiency). And the Tannoy driver he's using isn't one of the most efficient dual-concentric drivers.
Thanks for your reply!
And about transformers... I will have them custom made probably, from a great high quality italian manufacturer.
Maybe I should re-formulate my question:
I need more than 20W (more than 30W will be better), I'd like tubes but not expensive ones. I need low damping factor and I've got no "topology" or "operation class" fear.
What kind of amp do you suggest?
ErikdeBest said:
We tried some DIY and commercial stuff in the last months. Ming-Da 300B PP and a DIY 2A3 PP, some chinese 845 amp, DIY EL34 triode PP amp. No, we didn't try the same amp changing output tube mode of operation, because I think that an amplifier has to be designed for a choosen operation, and optimized for it. In fact, wiring in triode mode a Ming-Da EL34 PP (that was UL) sounded worse.
We even tried the ugly mono-channel prototype of my EL36 triode amp
ErikdeBest said:
Those are infinite baffle speakers. I'm not so expert in speakers matters, but as I understand that's not a "tube friendly" enclosure such as horn speakers (also because of lower efficiency). And the Tannoy driver he's using isn't one of the most efficient dual-concentric drivers.
Thanks for your reply!
And about transformers... I will have them custom made probably, from a great high quality italian manufacturer.
Maybe I should re-formulate my question:
I need more than 20W (more than 30W will be better), I'd like tubes but not expensive ones. I need low damping factor and I've got no "topology" or "operation class" fear.
What kind of amp do you suggest?
rdf, those cinemags look impressive.
But UTC and WE never tried to make high-bandwidth transformers. At least not by modern standard. The American film industry standard back in 1938 was a frequency response of 80-10,000 Hz for cinema amps. And that's basically what the 91A was designed for. It should reasonably have nothing to offer anyone today. That makes what they did back then all the more impressive in my opinion.
I don't think anyone believes people suddenly stopped making high-quality transformers. I would think that the only advantage of the old days was that transformers were mass-produced.
But UTC and WE never tried to make high-bandwidth transformers. At least not by modern standard. The American film industry standard back in 1938 was a frequency response of 80-10,000 Hz for cinema amps. And that's basically what the 91A was designed for. It should reasonably have nothing to offer anyone today. That makes what they did back then all the more impressive in my opinion.
I don't think anyone believes people suddenly stopped making high-quality transformers. I would think that the only advantage of the old days was that transformers were mass-produced.
My pick for amp to go with the Tannoys: British Radford STA-25. There was even a reissue some years ago.
STA-25
STA-25 Renaissance
STA-25
STA-25 Renaissance
phn said:
100% agree. Roundabout way of saying that in my opinion what made the old designs legendary wasn't so much iron as the genius and dedication of the designers working within their limitations. Back then, before the term was coined, audio designers were very much the 'rocket scientists' of the day. The field attracted the very brighest and best.
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